We have a user that has some issues with address cacheing which I have seen with my own eyes

To look into this I did a full device reload as a starter.

Testing, I typed an email address in and it was cached as expected. Then about two weeks later the cached address disappeared (as you would imagine since they would be cleared after a while), however if you type in the address and send to it again the address is not cached at all. This does not seem to happen to all addresses, only selected ones.

I realise the user can place the addresses in their contacts so it will always auto-complete however this would be cumbersome for the user.